Current practice in the automobile industry is to protect electrical and electronic equipment installed in automobiles by mean of fuses located in the fuse block in the glove compartment or under the dashboard of the automobile. These fuses are, for the most part, relatively low amperage and are designed to protect apparatus such as radios, lights, and turn signals. Also, these fuses operate in a temperature controlled environment since they are inside the passenger compartment of a car.
Many of the major electrical loads in an automobile are found underneath the hood of a car, such as the starter alternator, and the battery, to name several. These electrical apparatus draw relatively high currents compared to the typical fuse located under the dashboard. If these underhood electrical apparatus were to be protected by fuses mounted in the passenger compartment, the wiring connected to them would have to be routed through the firewall to the passenger compartment to the fuseblock and then back through the firewall to the component under the hood. This, of course, would add weight to the automobile, additional labor costs, and increase the cost of production. It is, therefore, desirable to locate some circuit protector under the hood of automobiles.
The automotive industry, in order to achieve weight reduction, is using smaller electrical cables with higher temperature insulation. A protective device to prevent the high temperature insulation from degrading due to high currents would have to open before cable insulation reaches damaging temperatures but not open on short duration current, overloads. Therefore, the automotive fuse must have certain time delay characteristics.
This fuse, or protective device, would need to operate in the engine compartment of an automobile where the ambient temperatures may range from a low of -40.degree. C. to a high of 145.degree. C. Because of these high temperatures it is desirable to have the plug-in terminals of fuses used to protect under-the-hood electrical equipment made of silver or plated with silver. The reason for this is that silver provides excellent electrical properties and also the oxide of silver are electrically conductive. However, if silver is used on the fusible element portion of the fuse, it will form a skin which adversely effects certain characteristics, such as ampacity, ampere capacity, of the fuse.
Other manufacturers have attempted to meet the requirements for silver plating on the fuse terminal portion without having silver plating on the fusible element by skiving or mechanically removing the silver plating from the fusible element. This is both time-consuming and adds additional costs to the manufacturing process. Other attempts to deal with the silver plating on the fusible element have used a slug or metal insert on the fusible element to compensate for the change in characteristics of the fusible element caused by the silver plating.
Another problem encountered in the manufacturing of large automotive fuses for use under the hood of automobiles has been marking an identification number or amperage rating on the fuses. In prior art methods, the fuse rating has been hot stamped onto the fuse housing. Because of the high temperature housing materials required in large automotive fuses, this has not been proved to be entirely satisfactory.